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By Martin A. Mayers

Five-sixths of all the coal that is mined in the United States is burned, without previous treatment other than screening, for the production of heat and power, so that its value is fixed by its suitability for this purpose. Nevertheless, the characteristics of individual coals that determine their fitness for use in particular pieces of combustion equipment are not yet well known. This condition is due not only to the small extent of our knowledge concerning coal itself, but also to our comparative ignorance of the nature of the combustion process. The following paper is an analysis of the combustion process as it occurs in industrial furnaces, based largely on the results of laboratory research on combustion rates. From this analysis it is possible to determine the characteristics of the fuel that limit the capacity of a given piece of combustion equipment. Limitations imposed by other factors than the attainable speed of combustion will not be considered, since they are subject to a different type of analysis involving the balancing of maintenance costs against fixed charges. In order to observe the relations among the various factors that affect the speed of combustion, representative particles of fuel will be followed through two types of furnaces. A pulverized-coal furnace will be considered first, because the independence of the individual particles facilitates the analysis of the effect of furnace conditions. The second example will be a grate-fired furnace in which ignition of the fuel takes place on the underfeed principle. This includes both underfeed and chain grate stokers, (8)† but does not include hand-fired furnaces and some overfeed stokers. The furnace will be considered to be large enough, the temperature high enough, and enough air provided, to burn the fuel completely, without, for the moment, specifying these quantities more completely. Furnaces Burning Pulverized Coal In a pulverized-coal furnace, the fuel particle is carried, in a stream of air, into the furnace, where it is subjected to radiation from the flame and from the hot walls of the furnace. The increase of particle tempera-

Jan 1, 1936

By Ilmar Stöckel, Gösta Harlin, Agne Rustan

INTRODUCTION This chapter is a continuation of the studies by Rustan and Stockel (1979, 1980) on techniques for automating ventilation in Swedish mines and construction works. The studies have been financed by the Swedish Board of Technical Development. As a result of the studies it has been recommended that a good solution to diesel exhaust emission would be automatic, step by step control of the fans near the working place. Diesel vehicles are the major polluters underground in the mines. Therefore, we have suggested that diesel vehicles regulate the fans The goal of the continued study has been to find a way for active diesel vehicles to start and stop gallery fans at both intake and return air. In this paper different methods for activating fans are discussed. The best methods are chosen and tested in the mine. In this study we have found that change of temperature is an inexpensive and effective way to start and stop crosscut fans in sublevel caving and radio signals seem to be an attractive system for starting and stopping gallery fans . This work has been done in close collaboration between LKAB in Kiruna and the University of Luleå, Divisions of Electronics and of Mining and Rock Excavation. An advisory group for the project has been established with ventilation experts from the mines, representatives of the local mine workers' unions, and authorities from the local offices of Governmental Inspection of the Workers Safety. VENTILATION SYSTEM STUDIED In the project the ventilation system at LKAB in Kiruna was studied. The mining method used is sublevel caving with 9-13 m slice height. The air above ground is heated in winter by hot water and the main fans push the air down to a main distribution level along the 4000 m long and about 100 m wide ore body. From the distribution level, air is taken through shafts down to the sublevels, where it is pushed through the levels by local gallery fans on both the intake and return sides, Fig. 1.

Jan 1, 1981

By Martin A. Mayers

Five-sixths of all the coal that is mined in the United States is burned, without previous treatment other than screening, for the production of heat and power, so that its value is fixed by its suitability for this purpose. Nevertheless, the characteristics of individual coals that determine their fitness for use in particular pieces of combustion equipment are not yet well known. This condition is due not only to the small extent of our knowledge concerning coal itself, but also to our comparative ignorance of the nature of the combustion process. The following paper is an analysis of the combustion process as it occurs in industrial furnaces, based largely on the results of laboratory research on combustion rates. From this analysis it is possible to determine the characteristics of the fuel that limit the capacity of a given piece of combustion equipment. Limitations imposed by other factors than the attainable speed of combustion will not be considered, since they are subject to a different type of analysis involving the balancing of maintenance costs against fixed charges. In order to observe the relations among the various factors that affect the speed of combustion, representative particles of fuel will be followed through two types of furnaces. A pulverized-coal furnace will be considered first, because the independence of the individual particles facilitates the analysis of the effect of furnace conditions. The second example will be a grate-fired furnace in which ignition of the fuel takes place on the underfeed principle. This includes both underfeed and chain grate stokers, (8)† but does not include hand-fired furnaces and some overfeed stokers. The furnace will be considered to be large enough, the temperature high enough, and enough air provided, to burn the fuel completely, without, for the moment, specifying these quantities more completely. Furnaces Burning Pulverized Coal In a pulverized-coal furnace, the fuel particle is carried, in a stream of air, into the furnace, where it is subjected to radiation from the flame and from the hot walls of the furnace. The increase of particle tempera-

Jan 1, 1936

By Frank Van Horn

IT is customary to ascribe two general modes of occurrence to natural gas, namely shale. gas which, as the name indicates, is found in' shale, and reservoir gas, which occurs ill sandstone, conglomerate and dolomitic limestone. Both of these types are found in the Cleveland district. The shale gas has been produced on a small scale for a long period of years, probably dating back as far as 1883. Shale gas is a low-pressure gas, small in volume with variable pressure, and is limited to no definite horizon. It is generally independent of oil, may last for a long time, and is not dependent to any great extent on the structure of the rocks. There are many such wells in the district which range from 400 to 1,840 ft. in depth, although most have been completed at about 800 ft. This indicates that the wells pass through the Cleveland and Chagrin shales into the Huron or Portage shale of the Upper Devonian. During the last 2 years great interest has developed in a deeper-seated reservoir gas. What is commonly called reservoir gas is generally a high-pressure gas occurring in large volume at a definite horizon. Oil may, or may not, be associated with the gas, and in most regions in which reservoir gas is found, the geological structure is of great importance. This type of gas occurs in all large fields such as those of West Virginia which have been supplying Cleveland until the recent discovery of local gas at great depths in commercial amounts.

Jan 1, 1917

By Jack Parker

There are some simple theoretical approaches to pillar design but they leave much to be desired. There are also more complex theoretical approaches, but at this time the most realistic approach is to go into the mines and observe and measure how real pillars are performing under real conditions; to allow the information thus gathered to ferment in our minds - then to project the behaviour of those pillars into our new designs and mining techniques, probably with no formulas at all. Examples, from half-a-dozen different mines, show how a simple- minded approach, through observation and measurement, led to changes in pillar design which often contradicted the textbook but made very significant contributions to mining safety, efficiency and costs. The good news is that we know a lot more about pillar design than we realize. We have, between us, looked at millions of pillars of all kinds, under all conditions, but we have overlooked what they are trying to tell us. We can take problem situations and turn them into opportunities and, in that way, become better stewards of the resources which have been given to us.

Jan 1, 1983

By Edward I. Salkovitz

RECENTLY a set of crystallographic angles for bismuth was calculated and a standard (111) projection was constructed. Since these calculations

Jan 1, 1957

By F. V. Lenel

Two years ago in Chicago a seminar was held on the theory of sintering of pure metal powders. As an introduction to this seminar D,.. Rhines1 gave an excellent survey of the literature on this subject, His method of presentatioll was to summarize the experimental observations on sintering and from them to develop a composite theory of sintering in which he combined all the important contributions to the theory into one organic whole. In contrast to the mechanism of sintering of pure metal powders, which, of course, al\vays takes place in the solid phase, sintering j,, the presence of a liquid phase, cannot be treated as one unified mechanism, such as the sintering mechanism of pure metals. The reason is that there are really several mechanisms depending upon the type of alloy system which is sintered and the field of its con. stitutional diagram ill which the sintering takes place, Two mechanisms have heen investigated and will be reviewed in this paper. Ill the first lnechanism the liquid is presellt during the entire time while the compacts are at the sintering temperature, In other words they are sintered between the liquidus and the solidus of the alloy system and are ~e~erogelleous during the entire sintering cycle. The second mechallism applies to alloys in which the liquid phase is formed during the sintering process, but disappears before the sintering process is completed through diffusion and formation of a solid solution. These alloys are therefore homogeneous at the end of the sintering cycle. This second mechanism is more complicated because of the two stages of sintering, the liquid and the solid, as they may be called. It is therefore not surprising that the few detailed investigations of sintering in the presence of a liquid phase have been concerned with heterogeneous sintered alloys, namely the tungsten-nickel-sinter ing which is the so-called "heavy alloy," and the cemented carbides. The mechanism of sintering of these systems is characterized by the fact that theoretical or near theoretical density is attained during sintering, while simultaneously a distinct grain growth takes place through solution of the smallest grains of the solid phase in the liquid phase and reprecipitation on the larger grains. In the first part of the survey this sintering mechanism which is called for short the heavy alloy mechanism is treated in detail. In the second part Of the survey experimental observations for the sintering of homogeneous sintered alloys where the liquid phase disappears before the completion of sintering are discussed. Much less systematic work has been done on these alloys to which the conlmercially important Porous bronzes and the iron-nickel-aluminum permanent magnet alloys belong. Emphasis will be laid throughout this survey upon the microstructural and density changes during sintcring because the Sintering mechanism can usually be described directly by these changes. Other

Jan 1, 1949

By N. A. Warner

Dense cylindrical specimens of artificial hematite were reduced in hydrogen over a range 0-f total pressures between 0.1 and 1.0 atm and temperatures between 650" and 950°C. Hydrogen reduction at a total pressure of 1.0 atm in the presence of a chemically inert diluent and reduction in hydrogen/water mixtures were also studied Znter.face movement during reduction was followed using metallographic techniques. Substantiu1 partial-pressure gradients are shown to exist in both the gas film and the reduced iron layer. The results are consistent with a mixed-control mechanism involving an interaction of gaseous-difusion effects with a first-order reversible chemical reaction at the iron/wüstite interface. Over the hydrogen-pressure range of 0.1 to 1.0 atm, the rate is not directly proportional to the hydrogen pressure in the bulk gas stream. Nitrogen dilution of the reducing gas masks the true effect of hydrogen partial pressure by influencing the effective molecular dif-fusivity and gives an apparent first-order relationship. The transport of hydrogen and water vapor across the iron layer is consistent with molecular gaseous diffusion rather than a Knudsen diffusion mechanism. ALTHOUGH the literature on the reduction of iron oxides is very extensive, it is only comparatively recently that a definite quantitative model for the reduction of hematite has been proposed. This development has been largely due to the work of McKewan. An extensive literature review of previous work has recently been compiled by Themelis and Gauvin. Exclusive control by gaseous diffusion in the reduction of hematite has been recently advocated by Kawasaki and coworkers.' Although the results of the latter workers are of considerable practical significance, the extreme porosity (approximately 30 pct) of their specimens precludes their application to a kinetic evaluation of the reduction of dense polycrystalline hematite. The salient features of the kinetic model used by McKewan for the gaseous reduction of dense hematite at temperatures in excess of 560°C (when FeO is stable) are: 1) The reduction is a topochemical reaction taking place through 'the series FeO/FesO4/FeO/ Fe; 2) The gas-solid type of reaction takes place only at the FeO/Fe interface and the internal reduction: FeO proceeds by solid state diffusion; 3) The iron layer formed is quite porous and offers negligible impedance to gaseous diffusion; 4) The rate-controlling step in the reduction is a chemical process occurring at the Fe/FeO interface. In view of the relatively fast reaction rates involved when hematite is reduced in a stream of hydrogen, it seemed possible that the simplifying assumptions of negligible diffusional resistance in both the bulk gas phase and the reduced iron layer could introduce serious errors in the interpretation of experimental reduction data. The present work was initiated to elucidate the effect of gaseous diffusion on the reduction rate and to determine its possible influence in the formulation of the reaction mechanism at the metal/oxide interface. EXPERIMENTAL Procedure and Apparatus. Dense cylindrical compacts of artificial hematite were prepared by sintering pressed compacts of reagent-grade ferric oxide, containing 99.6 pct FezO, in air at 1200°C for 80 hr. The resulting compacts had a final porosity of less than 2 pct and a height and diameter of approximately 1 cm. Variations in sintering atmosphere from air to pure oxygen, in sintering time from 20 to 80 hr, and temperature from 1150" to 1250°C had no effect on the subsequent reduction behavior. The reduction of the samples took place in a vertical tube furnace in which was placed a 1-in. transparent silica tube. The 24-in. heated length

Jan 1, 1964

By R. L. Fleischer, W. F. Hosford

Tensile data for coarse grained aluminum Polycrystals suggest that the "grain size" effect is not due to dislocations piled up at grain boundaries but rather is primarily a relative size effect due to surface crystals being weaker and less confined. STUDIES directed at interpreting hardening of poly-crystalline metals normally identify their strain hardening properties with those in some particular type of single crystal.1"4 The recent recognition in face centered-cubic metals of a nearly linear stage with rapid hardening occuring at comparable rates for both polycrystals and single crystals, suggested that the same process or processes determine both cases and hence that there exists some justification for the use of single crystals to understand polycrystals. Further evidence for the above view may be found by an approach initiated by Chalmers:5 By using bicrystals of controlled orientation it is possible to begin to assemble a polycrystal and also to study grain boundary effects in detail. In this way it has been found that a single grain boundary affects easy glide but not the subsequent stage II hardening.6 This result suggests that a sensitive way to observe grain boundary effects in polycrystals would be to vary grain size and measure easy glide. As will be seen, easy glide is only possible for coarse-grained samples, and hence the results will serve to fill in the gap in measurements between single crystals and bicrystals on one hand and fine-grained polycrystals on the other. One problem inherent in comparing single crystals with polycrystals is the uncertainty as to what slip systems are acting in a polycrystal. To compare the two types of samples, rates of shear hardeninn---L. on the acting -planes are needed. and these may be computed only if it is known what particular systems are active. The acting systems were examined for a coarse-grained polycrystal and it will be shown that the systems supplying the preponderance of slip can be determined with little ambiguity. EXPERIMENTAL PROCEDURE Twelve samples of aluminum were prepared by chill casting into a heated graphite mold, followed by annealing at 635° ± 5°C for 24 hr with an 8-hr fur- nace cool, and finally either etching7 or electropol-ishing.' The samples, with a 7 to 10 cm length between grips and 4.4 by 6.6 mm in cross section, were deformed at a strain rate of about 3 10 -3 . per min in a tensile device which has been described elsewhere.5 The composition was reported by Alcoa as 99.992 pct Al, 0.004 pct Zn, 0.002 pct Cu, 0.001 pct Fe, and 0.001 pct Si; nine samples were deformed while immersed in liquid helium and three in air at room temperature. The stress-strain curve for one of the samples (P-1) deformed at 4.2 "K has been reported previ~usl~.~ This sample was selected for determination of active slip systems. Eighteen of the crystals were examined by optical microscopy to determine the angles of slip line traces and by X-ray back reflection to determine orientation. By this means the slip planes were determined and the resolved shear stress factors for possible slip systems could be computed. Finally each sample was sectioned so that after etching, the number of crystals could be counted for each of ten newly exposed surfaces. The average of these ten values will be termed n, the number of crystals per cross section. Values of 11, varied from 1.9 (nearly bamboo structure) to 12.7. Sketches of typical cross sections appear in Fig. 1. RESULTS AND DISCUSSION: SLIP SYSTEMS 1) Determination of Acting Slip Planes—The stress axis orientation and operative slip planes in eighteen crystals of sample P-1, as determined by slip line traces and crystal orientation, are summarized in Fig. 2. For one of the crystals two planes had a common trace. so that the traces alone did not distinguish which plane or planes were slipping. However it was found that the stress resolving factor for the primary system was 0.386, .while that for the most stressed system in the other plane (indicated bv the dotted arrow) is 0.138. It will be assumed tgerefore that only the primary plane acted. Since the orientations were determined after extending the samples 4 pct, the stress axes may be rotated from their original value by as much as 2 deg in some cases. It is interesting to note that in five crystals only one slip plane acted, in eight two acted, and in five three planes were observed—an average of two slip

Jan 1, 1962

By M. E. Wadsworth, T. L. MacKay

Sintered UO, samples were leached in sulfuric acid solutions of various concentrations. A pressurized system was used so that it was possible to investigate the kinetics of the reaction to 270°C with oxygen overpressures as high as 900 psi. The rate was observed to be a function of the concentration of hydrogen ions and directly proportional to the partial pressure of oxygen. Evidences are presented which indicate that a UO2 surface site reacts with a molecule of water to form a hydroxyl complex which in turn can dissociate with the characteristics of a weak acid. A rate determining step has been proposed which involves the reaction between an oxygen molecule and the hydroxyl complex on the surface of UO,. ThE 2 principal methods for uranium dissolution are carbonate and acid leaching. The sulfuric acid leach is the more popular and is used for the treatment of the majority of the ores of Africa, Canada, and the United States. Low recoveries in basic leach circuits led investigators at the University of British columbia1 to study leaching of uranium ores in pressurized vessels. Early in the study of dissolution of uranium it was found that only uranium in the hexava-lent state could be leached in acid or basic circuits. Therefore, the use of oxygen over-pressure in an autoclave offered an interesting approach to solving the low recovery problems of carbonate leaching. UO, was used in this study because it could be obtained in high purity and also because it is representative of the most refractory of the primary uranium minerals. A pressurized system was used to provide a means whereby important temperature and pressure parameters could be varied for the evaluation of the kinetic processes. The mechanism for the dissolution of UO2 should be similar for any of the uraninite type minerals. At the present all of the kinetic studies that have been conducted have been in carbonate media. Peters and Halpern2 carried out a kinetic study of the leaching of pitchblende. Their specimens were pitchblende ores selected on the basis of high grade and homogeneity. Pearson and wadsworth3 conducted a kinetic study of the dissolution of UO2 in carbonate solutions with results very similar to those obtained by Peters and Halpern. EXPERIMENTAL The UO2 as received* was found by spectroscopic *Mallinckrodt reagent, supplied by the Atomic Energy Commission. analysis to have a purity of 99.94 pct 0.03. It was ground in a mechanical agate mortar and screened through a 400-mesh sieve. Thin flat disks of UO2 were prepared by pressing the sized powder in a specially constructed die at a total pressure of approximately 25 tons per sq in. The pressed disks were approximately 0.25 cm thick, 1.6 cm diam, and 3.5 g in weight. As pressed, the samples were approximately 65 pct of theoretical density. It was essential that a binder such as poly-vinyl alcohol be added before pressing to prevent formation of cracks when fired. It was found by trial and error that pressed disks sintered close to 1870°C in a hydrogen atmosphere, reach densities between 91 and 91.5 pct of the theoretical density. At this density the samples had no measurable porosity based upon a 2-hr emersion in boiling water. An X-ray examination of these sintered UO2 disks showed them to be identical with the original UO2 received. Reaction of UO2 with the alundum furnace core was prevented by placing molybdenum between the samples and the core according to the method of Corwin and Eyerly.4 Leaching studies were carried out in a specially designed autoclave, the details of which have been presented e1sewhere.6 The main features of the equipment as applied to a kinetic study are: 1) solution samples may be removed during the course of a single run; and 2) temperature and agitation are carefully controlled. Two-ml samples removed from the autoclave during the course of a run were analyzed for U3O8 content with a Beckman model DK-2 spectrophotometer by the method of

Jan 1, 1959

By R. H. Olds, B. H. Sage

The formation volume and volume of the liquid phase of oil and gas obtained from four fields in the San Joaquin Valley have been investigated at pressures, temperature, and gas-oil ratios comparable to those encountered in underground reservoirs. All the fields covered in this investigation yielded a product of a gas-oil ratio in excess of 5000 cu ft per barrel and the gravity of the tank oil for the four fields in question varied between 52° and 63' API. The results of the investigation, together with analytical data concerning the composition of the oil and gas, are submitted in tabular form. Rough correlations of the formation volume as a function of pressure, temperature, and gas-oil ratio and of the retrograde dew-point pressure as a function of gas-oil ratio, temperature, and gravity of tank oil are presented. It was not found feasible to correlate simply the formation volume of the liquid phase as a function of the applicable variable. It is desired to emphasize that these correlations are considered applicable only to the range of conditions covered in this investigation and for systems of similar nature and composition. Introduction Information concerning the physical properties of mixtures of oil and gas from particular fields have often been employed in predicting the situations obtaining in underground reservoirs. One of the earlier studies of this nature was the work of Beecher and Parkhurst,1 while a more recent study of the Dominguez Field2 presented detailed volumetric data in the two-phase as well as in the single-phase regions. Although these studies were confined to individual fields, their results proved of value in application to other fields. It has recently been shown 3,4 that it is possible in the region of low gas-oil ratios* to correlate the volumetric behavior of naturally occurring hydrocarbon mixtures from a single geographical area with sufficient accuracy to be of industrial value. For this reason it is considered of interest to submit information concerning the volumetric behavior of oil and gas mixtures from four different fields in the San Joaquin Valley and, in combination with similar published data5 concerning mixtures of oil and gas from the Paloma field in the same area, to show rough correlations between the composition and the behavior of materials from these fields. This effort seems particularly worth while since all of the

Jan 1, 1947

By C. L. Ray, R. E. Baarson, H. B. Treweek

As an example of nonmetallic mineral flotation, the separation of several pegmatite minerals will be discussed in considerable detail, from both the laboratory-testing and plant-operation standpoints. The pegmatites have been chosen to illustrate the practicality of the selective separations of the minerals in a complex nonmetallic ore and, in so doing, to set forth a summation of the flotation art and technology which is applicable in part to the beneficiation of several less complex nonmetallic ores. In addition, a brief summary of descriptions of other nonnietallic mineral flowsheets and separations is included. Some of the industrial minerals now being concentrated by froth flotation methods commercially, or in the laboratory, are listed in Table 1. GENERAL CONSIDERATIONS There are two classes of chemicals that are normally utilized as collectors in froth flotation separations of nonmetallic minerals. These are defined as anionic and cationic and are typified by the fatty acids and amines, respectively. The fatty acids are selective to those minerals that have a high concentration of positive surface charges, such as the various calcium minerals typified by calcite, phosphate rock, and fluorspar. The amines are selective to those minerals with a high concentration of negative surface charges, such as silica sand and silicates. It should be noted, however, that by using various inorganic chemicals, a new or synthetic surface can be placed on specific minerals which produces different characteristics, thereby reversing the flotation reagent required for separation. The polar end of the collector attaches to the mineral surface either by chemical or physical adsorption; the nonpolar unreactive end is oriented away from the mineral surface. The result is a hydrophobic coating at the mineral surface which causes attachment to air bubbles. It is this surface condition that permits the floating of minerals which normally sink in water. In order to utilize these fatty acids and amine derivatives, several conditions .must be fulfilled. Before there can be a selective flotation process,

Jan 1, 1962

By John E. Conley

THE production of lime by the burning or calcination of limestone, including all varieties from true dolomites and magnesian limestones to high-calcium types, continues as one of the essential basic industries. In 1937, a total of 4,124,165 tons of lime valued at approximately $30,091,000 was produced in the United States.1 The importance of any contribution to our knowledge on the mechanism of the lime-burning process is, therefore, obvious. The burning of limestone has been practiced since the earliest days of our civilization, and the literature on the various phases of the industry is voluminous. Calcination of the various types of limestone has been studied by many previous investigators, but some points require additional research. Each occurrence of limestone provides an opportunity for specific investigation, because the characteristics of stones in different localities vary Knibbs13 has given an excellent discussion of available data on the theory of lime and magnesia burning. The thermal dissociation of calcium carbonate has been studied more recently by Johnston,2 Smyth and Adams,3 Ralston et al.,4 Furnas,5 Potapenko,6 and Southard and Royster.7 As a result of these investigations the dissociation temperature at atmospheric pressure has been established as 894º to 898º C. The dissociation of dolomite and magnesite, although studied by several investigator,4, 6, 8 still requires clarification by additional data. The calcination of limestone was studied for a twofold purpose: (1) to extend our information on the mechanism of the lime-burning process and (2) to standardize the conditions for calcination of high-calcium and dolomitic limestones for subsequent hydration tests on the lime.

Jan 1, 1939

By Kenneth L. Cook

THE five serpentine masses exposed within the northern half of Riley County, Fig. 1, constitute a major part of the few exposures of igneous rock in Kansas.' Although not many subsurface data are available for this part of Riley County,2 six deep wellsV indicate that the basement complex lies between 2500 and 3000 ft below the earth's surface. A northwestward-trending ridge in the present basement surface, which extends across the northern half of Riley County, is indicated on Mettner's contour map.' The serpentine masses lie in a region that was active during Pennsylvanian and Permian time along two main tectonic trends, which may, in part at least, have developed contemporaneously." One trend is northeasterly, as evidenced by the Nemaha anticline, the Abilene anticline, the Voshell anticline, and many other smaller northeastward-trending folds. The other trend is northwesterly, as evidenced by the central Kansas uplift, the Salina basin syncline, and smaller northwestward-trending folds. The area of the Abilene anticline was actively deformed during much of this time, and the present surface rocks, for the most part Permian in age, show many normal faults." The Bala and Leonardville intrusions lie within a mile of the axis of the Abilene anticline, Fig. 1, as mapped by Wallace Lee;' the Randolph No. 1 and Randolph No. 2 intrusions lie within about 5 miles of the axis; and the Stockdale intrusion lies within about 8 miles of the axis. The igneous rocks have intruded horizontal or gently dipping limestones and shales that are late Permian in age.V he period of intrusion, according to Moore and Landes, was probably Cretaceous.' At present a detailed description of the petrography is available for only the Bala intrusion. Moore and Haynes' describe the rock at Bala as a green, serpentinized, porphyritic, peridotite breccia containing inclusions of shale. The ground mass consists chiefly of serpentine and calcite with considerable chromite (5 to 10 pct) and some magnetite. The phenocrysts consist principally of altered olivine with some altered augite and biotite. Although probably different in petrographic details, all the serpentine masses are somewhat similar in that 1) they consist of a dark green, fine-grained ground mass of igneous rock containing many xeno-liths composed of fragments of the neighboring sedimentary rock; 2) they tend to form small mounds on the landscape, thus indicating their greater resistance to weathering and erosion; and 3) they are magnetic. Previous Magnetic Survey of the Bala Intrusion: To the writer's knowledge, only the Bala intrusion had been surveyed with a magnetometer prior to the magnetic surveys discussed in this paper. Dreyer8 interprets the intrusion as a vertical, eastward-plunging dike, on the basis of the results of his magnetic survey, Fig. 1, with a vertical magnetom-

Jan 1, 1956

By R. H. Olds, B. H. Sage

The formation volume and volume of the liquid phase of oil and gas obtained from four fields in the San Joaquin Valley have been investigated at pressures, temperature, and gas-oil ratios comparable to those encountered in underground reservoirs. All the fields covered in this investigation yielded a product of a gas-oil ratio in excess of 5000 cu ft per barrel and the gravity of the tank oil for the four fields in question varied between 52° and 63' API. The results of the investigation, together with analytical data concerning the composition of the oil and gas, are submitted in tabular form. Rough correlations of the formation volume as a function of pressure, temperature, and gas-oil ratio and of the retrograde dew-point pressure as a function of gas-oil ratio, temperature, and gravity of tank oil are presented. It was not found feasible to correlate simply the formation volume of the liquid phase as a function of the applicable variable. It is desired to emphasize that these correlations are considered applicable only to the range of conditions covered in this investigation and for systems of similar nature and composition. Introduction Information concerning the physical properties of mixtures of oil and gas from particular fields have often been employed in predicting the situations obtaining in underground reservoirs. One of the earlier studies of this nature was the work of Beecher and Parkhurst,1 while a more recent study of the Dominguez Field2 presented detailed volumetric data in the two-phase as well as in the single-phase regions. Although these studies were confined to individual fields, their results proved of value in application to other fields. It has recently been shown 3,4 that it is possible in the region of low gas-oil ratios* to correlate the volumetric behavior of naturally occurring hydrocarbon mixtures from a single geographical area with sufficient accuracy to be of industrial value. For this reason it is considered of interest to submit information concerning the volumetric behavior of oil and gas mixtures from four different fields in the San Joaquin Valley and, in combination with similar published data5 concerning mixtures of oil and gas from the Paloma field in the same area, to show rough correlations between the composition and the behavior of materials from these fields. This effort seems particularly worth while since all of the

Jan 1, 1947

By R. S. Cartwright

TWO types of automatic drilling controls, the Halliburton and the Hild, are now available and are coming into more or less general use in deep drilling. The primary function of both is to maintain a safe limit of torque on the drill pipe, this being accomplished by automatically controlling the weight or pressure on the cutting tool. Neither type will necessarily increase drilling speed, but by permitting advantage to be taken of "breaks" in the hole higher average cutting speed may be maintained. The control is essentially a safety device, and should be considered as such. It is not the purpose of this paper to discuss the merits of drilling controls, although the advantages over manual feed at the brake drum are obvious, but rather to point out some of the limitations. The Halliburton Control The Halliburton control is designed to operate during drilling through the agency of the draw works. Automatic and constant control of the torque on the bit is governed by clutches on the control itself, and the line shaft to drum shaft drives on the draw works. In operations other than drilling the control is simply a jackshaft between prime mover and draw works. It is, of course, adaptable to any type of power. Because control of the torque on the bit is dependent on the various ratios or clutch combinations available on the Halliburton control and the draw works, it follows that there are certain limitations in points of control. Table 1 shows the possible ratios which can be obtained with the control and a popular type of three-speed draw works, it being assumed that the highest possible gear combination—the combination which when engaged will suspend the least amount of weight—has a value of 1.00. According to the table there are "blind spots" in the series. This is true particularly among the lowest ratios, which are most used to suspend the major part of the weight when great depths are reached. It will be noted that there is a difference of nearly three units in the value of the

Jan 1, 1929

By C. P. Proctor, J. T. Crawford

TROUGH washers were among the earliest methods used for concentrating ores; they are referred to by Agricola about the middle of the sixteenth century as already being used while the hand- operated jigging sieve had only recently come into use. For cleaning coal the trough washer apparently was first used in France and Belgium about 1841. The early trough washers were intermittent and the refuse at least was shoveled out by hand. The invention of a continuous jig washer, by a Frenchman, Berard, in 1848, acted as a stimulus to coal washings in jigs and retarded progress in trough washing in the nineteenth century. Chapman and Mott' describe a number of trough washers developed in England and on the Continent from 1850 to 1900, such as the Bell and Ramsay, Ramsay, Bell and Green, Wunderlich, Scaife, McLellan, Lodge, Elliott, Blackett, and Murton. The later of these removed the refuse mechanically, either intermittently or continuously, but in ways that interfered with stratification.

Jan 1, 1943

By Ernest Gayford

When the United States Government started buying gold at varying prices per ounce, set by the President and the Treasury Department, the gold miner found himself facing new conditions, as gold became a commodity with a fluctuating market price. While it was self-evident that the miner was to receive more for his gold than the old established price of $20.67 per ounce, there was an element of uncertainty, which made it difficult, and perhaps dangerous, to decide to invest his time and money to produce gold, especially if the profit would represent only the difference between $20.67 an ounce and the new price as set from day to day by the Government. When, however, on Jan. 30, 1934, the United States went off the gold standard, the price of newly mined gold being rather definitely set at $35 per ounce, with some assurance that the price would be maintained at or near this figure for a long time to come, the gold miner was justified in revaluing his property on the basis of the new price, and the prospector was offered inducement to spend his time and energies hunting for new mines, or going back to old locations previously abandoned as of doubtful value. It is interesting to see what this new price means to the producer of newly mined gold, and how much of the increase is passed on to the producer. It will be found that, as with the base metals, the nearer he can get to producing a finished product himself the greater his reward will be; the net returns for bullion being necessarily higher than for the same amount of gold shipped in concentrates to the smelter. Bullion can be shipped to the United States mints or Government assay offices under the following terms and conditions. An affidavit must accompany the shipment, stating, among other things: 1. The source of the gold; whether ore, tailings or placer. 2. The tons of ore, tailings or cubic yards of gravel from which the shipment was recovered.

Jan 1, 1935

By J. B. Austin

MEASUREMENTS of the rate of decomposition of austenite at constant temperature are commonly represented by plotting the percentage trans-formed on linear coordinates against time on either a linear or a logarith-mic scale, a method that yields a curve that in shape resembles an integral sign (Fig. 1). A graph of this kind is not always convenient because extrapolation to the beginning or end of the transformation, or even inter-polation, may be uncertain unless there are a large number of observations, which seldom happens; furthermore, the degree of consistency of a set of measurements is difficult to judge from such a curve. It is desirable therefore to find some mode of plotting, or even better to find a standard variety of graph paper, that gives a straight line instead of the integral shape. The straight line has many advantages; the number of readings required to fix the position of the curve is greatly reduced, interpolation is easy and rapid, extrapolation can be carried out with greater confidence and, finally, the consistency of the measurements is readily estimated from the scatter of the points. The last advantage is particularly valu-able when the data are obtained by direct microscopic examination alone, because they are influenced by the skill of the observer in estimating the relative size of areas, possibly also by undetected inhomogeneity of the specimen. A search for ways of representing the observations as a straight line yielded two methods which are described in this paper. The paper also includes an account of some interesting relations brought to light in applying these methods to the available experimental data. Usually the best way to derive such a method of plotting is to base it on established principles of chemistry and physics, as has been done, for example, for the temperature variation of the equilibrium constant of a chemical reaction. But so little is known of the mechanism of the decom-position of austenite, and so little is available in the way of well established background for changes of this kind, that it is simpler to rely upon purely empirical means. The general plan therefore is to study existing data with a view to finding some function of the direct observations that will

Jan 1, 1938

By W. H. Emmons

IN 1922 Morey made a series of experiments in which he observed the cooling of a molten system containing H20, 9.1 per cent; K20, 17.3 per cent and Si02, 73.6 per cent. This system was confined in a bomb; it was fluid at 500° C. and exerted no vapor pressure. In cooling to 420° C. a large part of it crystallized and at that temperature much of the water had separated from the crystals and remained as steam, which built up a pressure of 4998 lb. per sq. in., a force sufficient to lift nearly one mile of granite.1 If granite, cooling at 600°, expels vapor in the process of crystalliza-tion it is reasonable to suppose that a considerably greater vapor pressure would result, and it is thought that the vapor expelled from crystallizing granitic batholiths probably has a pressure sufficient to lift two or three miles of granite. This vapor, collecting near the tops of cupolas of batholiths, is believed to exert sufficient pressure to fracture the hoods and roofs of batholiths above the cupolas. If that is true, one would expect to find that the fracture systems above cupolas are arranged in patterns that depend in part on the shapes of the cupolas. The mechanics of the situation seem to require that conical cupolas should have radial fracture patterns, that bluntly rounded cupolas should have fracture systems that are either irregular or rudely conjugated in plan, and that elongated stocks or cupolas should have fracture systems in which the fractures lie nearly parallel to the direction of the elongation of the cupolas.

Jan 1, 1934